The invention relates to carbohydrate paclitaxel and docetaxel derivatives to increase their solubility in water.
Paclitaxel is a natural product extracted from the bark of the Pacific yew (Taxus brevifolia). It was thereafter found in other members of the Taxacae family including the yew of Canada (Taxus canadensis) found in Gaspesia, eastern Canada and Taxus baccata found in Europe whose needles contain paclitaxel and analogues and hence provide a renewable source of paclitaxel and derivatives. The crude extract was tested for the first time during the 60s and its active principle was isolated in 1971 by Wani et al. (Wani et al., J. Am. Chem. Soc. 93:2325-2327, 1971) who at the same time identified its chemical structure. It showed a wide range of activity over melanoma cells, leukemia, various carcinomas, sarcomas and non-Hodgkin lymphomas as well as a number of solid tumors in animals. Docetaxel is the active ingredient of Taxotere(trademark) originally developed by Aventis Pharmaceuticals. It is prepared by semi-synthesis from 10-Deacetylbaccatin III, a taxane abundant in the European yew Taxus baccata. Taxotere is currently approved in the United States to treat patients with locally advanced or metastatic breast cancer after failure of prior chemotherapy and for treatment of non-small cell lung cancer. Clinical studies have shown that paclitaxel and docetaxel are very effective anti cancer agents. They are both microtubule blockers, but unlike other drugs inhibiting the mitosis by interaction with microtubules such as colchicin, vincristin and podophyllotoxin, paclitaxel and docetaxel do not prevent tubulin assembly. They rather accelerate the tubulin polymerization and stabilize the assembled microtubules. The drugs act in a unique way which consists in binding to microtubules, preventing their depolymerization under conditions where usually depolymerization occurred (dilution, calcium, cold and microtubules disrupting drugs). Paclitaxel and docetaxel block the cell cycle at prophase which results in an accumulation of cells in G2+M. Because of their unique structures and mechanism of action, paclitaxel and docetaxel were submitted to clinical trials. Interesting activity against many tumors, especially breast cancer and ovarian cancer refractory to chemotherapy, has been observed. However, because of its poor solubility in water, paclitaxel had to be administered in ethanol, Cremophor-EL and 5% sucrose diluted in saline or water. Cremophor-EL was responsible for hypersensitivity reactions observed in several patients (Rowinsky, E. K., et al., J. Nat. Can. Inst., 82 (15), 1247-1259, 1990). Premedication with anti-histamines had to be administered in order to reduce the toxicity.
Poor solubility of paclitaxel constitutes an important limitation to its administration to cancer patients. To increase paclitaxel availability, total and partial syntheses have been reported. The improvement of paclitaxel solubility was obtained by adjunction of solubilizing functions such as carbonyl or sulfonyl groups with good results. Some of the synthesized products were more active than paclitaxel, many others had a biological activity equivalent or slightly inferior to that of paclitaxel while being far more soluble in water (Kingston. D. G., Pharmacol. Ther. (England), 52(1) p1-34, 1991). The complexity of the paclitaxel chemical structure rendered its total synthesis very difficult but it was achieved simultaneously by two different groups. However the yield of this synthesis of the order of 2-4% will have little impact on the paclitaxel availability (Borman, S., Total synthesis of anticancer agent paclitaxel was achieved by two different routes (Borman et al., 1994, C and EN, 21:32-4)).
Many attempts have been made to improve paclitaxel aqueous solubility with various components resulting in poorly stable products, inactive ones or derivatives which upon metabolism yielded undesirable side products. Moreover, sometimes the synthesis of these compounds required many chemical steps.
Paclitaxel has three hydroxyl groups at carbon 1, 7 and 2xe2x80x2 susceptible of undergoing an acylation. Their reactivity varies according to the following order: 2xe2x80x2 greater than 7 greater than  greater than  greater than 1 (Mathew, A. E., et at., J. Med. Chem., 35, 145-151, 1992). Acylation on C2xe2x80x2 is the best way of paclitaxel modification because of its great reactivity, and because even if 2xe2x80x2 acylpaclitaxels loose their property of promoting the microtubules polymerization in vitro, they are hydrolyzed in the cell and revert to paclitaxel and keep their cytotoxic activity (Kingston et al., 1990, J Nat Prod, 53:1-12; MELLADO, W., et al., Biochem. Biophys. Res. Commun., 105: 1082-1089, 1984; Bicamumpaka C. and Page M. Oncol Rep. 1998 November-December 1998;5(6);1381-3; and Jaime J. and Page M. Anticancer Res. 2001 21(2A):1119-28.
Accordingly, to increase solubility, several derivatives have been synthesized by modification of the 2xe2x80x2 or/and 7 hydroxyls. The 2xe2x80x2 hydroxyl appears as a good candidate for chemical modification. The 7 hydroxyl requires more drastic conditions to react while the tertiary hydroxyl in position 1 is inert. The 2xe2x80x2 and 7 hydroxyls have been modified by several groups (Deutsch, H. M., et al., J. Med. Chem., 32: 788-792, 1989: Rose, W. C., et al., Cancer Chemother. Pharmacol., 39: 486, 1997 and Bicamumpaka C. Page M. Oncol Rep. November-December 1998;5(6):1381-3. and Jaime J. and Page M. Anticancer Res. 2001, 21(2A):1119-28), but only a few derivatives were synthesized with a sugar moiety as reported by Kingston et al. (Kingston, D. G. I., Pharmac. Ther., 52: 1-34, 1991). However, many derivatives were insufficiently soluble, inactive or too unstable to be applied in a clinical situation.
Carbohydrates are very soluble in water and they are used by nature in the form of carbohydrate conjugates to eliminate some non-soluble metabolites.
It would be highly desirable to be provided with new active paclitaxel and docetaxel derivatives to increase the solubility of paclitaxel and docetaxel in water while, upon hydrolysis, and which derivatives produce non-toxic side products.
One aim of the present invention is to provide new paclitaxel and docetaxel derivatives modified at least at one of 2xe2x80x2- and 7 positions to improve their solubility.
Another aim of the present invention is to provide carbohydrate derivatives of paclitaxel and docetaxel which upon degradation yield non toxic carbohydrates and the original paclitaxel and docetaxel molecules.
Another aim of the present invention is to provide a method for the in vivo treatment or prophylaxis of cancer comprising the step of administering a therapeutically effective amount of a water-soluble paclitaxel or docetaxel derivative as defined above to a patient in need of such a treatment.
Another aim of the present invention is to provide a method for the in vivo treatment or prophylaxis of skin diseases comprising the step of applying topically a therapeutically effective amount of a water-soluble paclitaxel or docetaxel derivative as defined above to a patient in need of such a treatment.
In accordance with the present invention there are provided new paclitaxel and docetaxel derivatives or salts thereof having the following Formula I: 
Wherein R and R1, identical or different, are a hydrogen or COxe2x80x94(CH2)nxe2x80x94COxe2x80x94X in which n is 2 to 14 and X is a carbohydrate such as a monosaccharide, a disaccharide or a polysaccharide, an amino sugar or an amino acid and wherein R2 is a hydrogen or acetyl and R3 is phenyl (in the case of a paclitaxel derivative) or t-Butyloxy (in the case of a docetaxel derivative).
In one embodiment, R and R1 interchangeably are a hydrogen and COxe2x80x94(CH2)nxe2x80x94COxe2x80x94X in which n is 2 to 14 and X is selected from the group consisting of D-glucosamine, D-galactosamine, mannosamine, fucosamine, lactosamine, mycosamine and muramic acid.
In a further embodiment, R and R1, identical, are each COxe2x80x94(CH2)nxe2x80x94COxe2x80x94X in which n is 2 to 14 and X is selected from the group consisting of D-glucosamine, D-galactosamine, mannosamine, fucosamine, lactosamine, mycosamine and muramic acid.
In another embodiment, R and R1 interchangeably are a hydrogen and COxe2x80x94(CH2)nxe2x80x94COxe2x80x94X in which n is 2 to 14 and X is a natural or synthetic polymer of amino sugars consisting of 2 to 100 units of D-glucosamine.
In still one embodiment of the invention, R and R1 are each COxe2x80x94(CH2)nxe2x80x94COxe2x80x94X in which n is 2 to 14 and X is a natural or synthetic polymer of amino sugars consisting of 2 to 100 units of D-glucosamine. Preferably, the polymer of amino sugar is identical on R and R1.
In a further embodiment, R and R1 are interchangeably a hydrogen and COxe2x80x94(CH2)nxe2x80x94COxe2x80x94X in which n is 2 to 14 and X is a natural or partially digested chitosan. Preferably, R and R1, identical, are each COxe2x80x94(CH2)nxe2x80x94COxe2x80x94X in which n is 2 to 14 and X is a natural or partially digested chitosan.
Yet in a further embodiment of the invention, R and R1 are interchangeably COxe2x80x94(CH2)nxe2x80x94COxe2x80x94X in which n is 2 to 14 and X is selected from the group consisting of D-glucosamine, D-galactosamine, mannosamine, fucosamine, mycosamine and muramic acid and COxe2x80x94(CH2)nxe2x80x94COxe2x80x94X in which n is 2 to 14 and X is selected from the group consisting of asparagine, glutamine and lysine.
Preferred amino acid that can be used in accordance with the present invention include, without limitation, asparagine, glutamine and lysine.
In another embodiment of the invention, R and R1 are interchangeably COxe2x80x94(CH2)nxe2x80x94COxe2x80x94X in which n is 2 to 14 and X is a natural or partially digested chitosan and COxe2x80x94(CH2)nxe2x80x94COxe2x80x94X in which n is 3 to 8 and X is selected from the group consisting of asparagine, glutamine and lysine.
Still in accordance with the present invention, there is provided a polymeric compound comprising 2 to 100 units of D-glucosamine, each unit bearing a compound of formula II: 
wherein R2 is a hydrogen or acetyl and R3 is phenyl or t-Butyloxy and wherein R and R1 are interchangeably COxe2x80x94(CH2)nxe2x80x94COxe2x80x94X in which n is 2 to 14 and X is a bond attaching the compound of formula II to a nitrogen of the glucosamine and a hydrogen.
In one embodiment, R and R1 are interchangeably COxe2x80x94(CH2)nxe2x80x94COxe2x80x94X in which n is 2 to 14 and X is a bond attaching the compound of formula II to a nitrogen of the glucosamine and COxe2x80x94(CH2)nxe2x80x94COxe2x80x94X in which n is 2 to 14 and X is selected from the group consisting of asparagine, glutamine and lysine.
In accordance with the present invention, there is further provided a chitosan derivative consisting of a natural or partially digested chitosan bearing one more units of the compound as defined above wherein X is a bond attaching the compound to a nitrogen of said chitosan and R1 is a hydrogen.
Sugars that can be used in accordance with the present invention include without limitation, glucose, mannose, galactose, arabinose, lactose, fructose, xylose, sucrose, fucose, raffinose, rhamnose, melibiose, stachyose and maltose.
In another embodiment of the invention, X can also be a mono-, di- or polysaccharide.
Also in accordance with the present invention, there is provided a polysaccharide consisting of 2 to 100 units of monosaccharide bearing 2 to 100 units of the compound as defined previously, wherein X is a bond attaching said compound to said polysaccharide.
In accordance with the present invention, there is also provided a method for the in vivo treatment or prophylaxis of skin cancer comprising the step of administering a therapeutically effective amount of a water-soluble paclitaxel and docetaxel derivatives as defined above to a patient in need of such a treatment.
For the purpose of the present invention the following terms are defined below.
The expression xe2x80x9camino sugarxe2x80x9d is for example intended to mean without limitation any carbohydrate having an amino group attached thereon by a covalent bond.